It might be possible, but you won't get far anyway: there is minimal
work to get done (mostly code refactorization) before PV drivers can be
used under a HVM domain.

Minimal you say? How much might it cost? I haven't the time to learn
Xen internals and do it myself, but I have been planning to donate some
money...

This is the kind of stuff you do when you want to have the "best of both
worlds": memory is managed at hardware level via HVM, and devices use PV
to avoid emulation overhead. As NetBSD got PV support very early, there
wasn't much push to mix HVM and PV; we will get there eventually though.

Totally. In my case I want to use it for builds, so I want fast IO
_and_ MP. I think I will try a test tonight... build the kernel in both
environments, and see which one is faster.